This is variation of Ralph Cutter’s E/C Caddis, which has been around since 1981. I have had a lot of success with Yellow Humpys, when Tan Caddis are emerging, so this pattern, in what amounts to a “dirty yellow’ once the Nano Silk is wrapped around the hook shank, follows that line of reasoning and this design sits lower in the surface film. E/C stands for “emerger/cripple” – it is a proven design. Charlie Craven ties it http://www.charliesflyboxinc.com/